text:
What is the belly pod on this Beech A200 Super King Air?
In this photo of N46L, a Beech A200 Super King Air owned by Dynamic Aviation, there is a large pod attached to the belly with what looks like two largish ports or windows on the underside.  What is it, exactly?  It looks similar to a synthetic aperture radar pod or video surveillance package, but I was curious if anyone could ID it precisely.

The full photo is available at http://www.jetphotos.net/viewphoto_new.php?id=7118680.

Looking at the full photo, it appears there's also a non-standard installation on the belly aft of the pod and possibly something other than a pitot tube on the right upper part of the nose.

Good catch--if anyone knows what those are I'd like to know!

Short answer
It seems to be a US Army CEASAR pod, a communication intercepting and jamming system for electronic warfare, which has been flown in Iraq and Afghanistan. CEASAR is derived from AN/ALQ-227 EA used by US Navy on the EA-18G Growler.
The aircraft is equipped with missile detection and countermeasures. Two sensors are below the cockpit windscreen, two other on the aft fuselage. The chaff is released by a dispenser aft of the pod.
N40R is N46L's sister aircraft, and it also carries a CEASAR pod. The A200 variant used may be a C12-A or a C-12C (this is the model number visible on N40R fuselage). They are also known as Huron and HC-12.
High definition photo of N46R:

Photo by Keith Newsome on photobucket (source)
Detailed answer below.

About CEASAR
From Stars and Stripes:

The CEASAR, which stands for communications electronic attack with
surveillance and reconnaissance, is a rectangular metal box that holds
technology capable of both knocking out cell phones and radios and
intercepting transmissions, while an electronic warfare officer
onboard speaks directly to troops on the ground. It’s precise enough
to cover friendly soldiers while jamming insurgents, but not knocking
out communications for an entire village near a given operation.

From matthewaid.com:

Contractors Continue Flying CEASAR SIGINT Aircraft in Afghanistan
The CEASAR system mounted in these contractor-owned and
government-operated (COGO) aircraft is based on the Raytheon
AN/ALQ-227 EA system as fitted to the US Navy’s (USN’s) Boeing EA-18G
Growler electronic warfare (EW) aircraft. It is designed to provide
both a communications jamming and an intercept/monitoring capability.

CEASAR UAV replacement
Flying CEASAR on a modified A200 was already very much cheaper than using a pod on a fighter. However like for other functions, military are looking at using unmanned aircraft. The NERO pod has been designed for this purpose.
From Defense Systems:

NERO jams aboard a drone in Army test
The Army recently tested a jammer called the Networked Electronic
Warfare Remotely Operated, or NERO, attached to a Gray Eagle unmanned
combat aircraft at the Great Salt Lake Desert at Dugway Proving
Ground, Utah.

Missile Warning System AN/AAR-47
Closer view (N40R):

It detects infrared or radio sensing from a missile and commands a response, e.g. release of chaff or flare using the countermeasures dispensing system aft of the pod.
Two other sensors are located on the aft fuselage.
Sensor detail on another aircraft:

(source)

About the aircraft
From FAA, King Air A200, CN BC-1 thru BC-61 are variant C-12A used by US Army.
From JetPhotos.net this aircraft is used under call-sign Grizzly 23:

Registration: N46L
CN: BC-56
'Grizzly 23' taxies for departure to Wick.this is one of a number of
aircraft owned by Dynamic that operate on behalf of the US Army.

There are two C-12 aircraft equipped with CEASAR. The other is registered N40R, with call-sign Grizzly 12:

(source)
Huron are seconded or being replaced by Dash 8.

Excellent job tracking that down, thanks!

Excellent answer yet again!  In my opinion, one of the best on this site!


text:
Effect of leading edge contamination wing performance
When a wing accumulates irregularities such as insects or dirt on the leading edge, its performance decreases. There are two main effects of this which are explained in https://aviation.stackexchange.com/a/16956/63452.
However, I do not understand is why stall angle and lift coefficient are reduced. That is, at sufficiently high Re (3e6, very common in aerospace applications) the boundary layer becomes turbulent, regardless the presence of contamination, almost directly at the leading edge at moderately high angles of attack (10 degrees).
What is the reason that a contaminated airfoil stalls earlier given that the boundary layer characteristics are the same?

At those Reynolds numbers and AoA a modern airplane should have some 20 to 50% of the chord with laminar boundary layer, so dirt can make a difference.

Oke, suppose we increase the aoa to 10 degrees. XFOIL shows transitioning at 0.02c for NACA4412 at Re = 3e6. This is also the region where stall is starting for contaminated leading edges and not for clean leading edges. PS I made an edit to the question for this case

Well, I think that the answer you linked answers in a very good way your question. Turbolent boundary layer implies higher quantity of air's speed which is eaten up by viscous friction. This gives both higher drag and less inertia against rise of pressure in the aft part of the airfoil which is what cause stall. Dirt, promoting an earlier transition from laminar to turbolent, makes these effects worse.

As I mentioned, the transition happens almost instantly. Therefore, how can dirt 'turbulate' the already turbulent boundary layer and thereby change the stall behaviour?

Dirt accumulates on the leading edge and therefore it "turbulates" the laminar part of the boundary layer, not the already turbolent one. This makes the airfoil stall a couple of degrees in advance and at a lower lift coefficient and higher drag coefficient.

Some airfoils, especially supercritical ones that develop separation bubbles at high AOA, can barely tolerate ANY contam anywhere above the stagnation point. The non-slat CRJs and Challengers have sep bubbles, and light morning frost on the LE is enough to bring one down on takeoff as stall AOA is reduced to about 9 deg, and the bubble results in instantaneous stall of the entire wing at once when it does let go. There was a CRJ crash in China from taking off on a bright clear morning with just some frost on the LEs that the crew thought was not a big deal.

@sophit, are you sure? This implies that at a.o.a. = 10 deg the effect of the very small laminar BL (recall up to x/c = 0.02) becoming turbulent (say at x/c = 0.0) has such immense effect?

This implies that the boundary layer transitions to fully turbulent at say 6° instead of 10° and the airfoil stalls at 14° instead of 16° and with a $C_d$ of 0.06 instead of 0.03

The canard on Rutan Long EZs, as originally designed, is infamous for this. On almost any amount of precipitation, it would rapidly experience a drop in lift coefficient. Because the elevator is on a canard,  and the lift generated there controls the pitch trim force, the aircraft would immediately pitch down, and, (if sufficiently above canard stall speed), the pilot would have to apply additional elevator (back stick), to reestablish pitch attitude.

If close to canard stall, the change would result in canard stall, but the resulting nose drop would lower canard AOA and it would begin flying again. If the pilot held full aft stick pressure, it would stall again, and the aircraft would enter a continuous cycling nose bobble, up and down, as the canard would stall, fly again, stall, and fly again, over and over in a 2-3 second oscillation. This was not dangerous, unless you were in the flare close to the ground, as the aircraft would lose 8-10 feet with each bobble.

Back in the day, there was a story told about even further back that there was an extremely nervous passenger on a DC-9-10 awaiting takeoff in cold, precipitating weather. The stewardess tried to reassure the passenger, who raised his voice, "I'm Mr. Douglas and I know how these planes without leading edge slats might be affected in weather like this!" (or something like that)

There are leading edge OML variations that can cause premature boundary layer transition and then there are VARIATIONS that can cause premature boundary layer separation. Even if the extent of laminar flow is unaffected, other BL characteristics can be. Sometimes, these are by design. For example, stall strips to force the inboard part of a wing to stall before the outboard.

What is the reason that a contaminated airfoil stalls earlier given that the boundary layer characteristics are the same?

But they are not the same!  This problem had already been studied to death by at least 50 years ago, and now there has been nearly a century of study on exactly this problem. F.X. Wortmann has commented on this before saying that the issue lies with the fact that the laminar boundary layer downstream of the instability point is a strong amplifier for incoming perturbations.  Wortmann makes note of a rather startling fact:  'If we compare the roughness height, which will not shift the transition and not increase skin friction, we find for higher Reynolds numbers that the turbulent boundary layer requires usually a smoother surface than the laminar flow…’
In particular, if the laminar boundary layer is prematurely tripped to become turbulent, the relationship between momentum thickness and displacement thickness becomes altered and the turbulent boundary layer becomes loaded by the intense pressure gradient.  Consequently, the turbulent boundary layer can no longer remain attached against the increasing pressure gradient and therefore becomes abruptly detached.  As Wortmann notes, ‘[t]his… example illuminates the well-known fact that changes in surface condition and hence boundary layer condition at the nose [of the airfoil] can have drastic effects near maximum lift. Sometimes one [wishes the] designer[s], builders and users of aircraft would be more aware of this fact.’
Reference: Wortmann, FX, 1976. Airfoil Synthesis Techniques. Institut fur Aerodynamik und Gasdynamik, Stuttgart, in cooperation with Department of Aerospace Engineering, University of Texas, Arlington. A scanned third-order copy with Wortmann’s hand-written margin notes, is available on the internet. Read carefully and understand the math.  Richard Eppler has also exhaustively investigated turbulent separation.

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

sort: votes


text:
Is ADS-B anonymous mode deterministic?
From what I can tell, this is the method of creating a temporary ICAO address in the 978Mhz UAT protocol:
From https://www.icao.int/safety/acp/Inactive%20working%20groups%20library/ACP-WG-C-UAT-2/UAT-SWG02-WP04%20-%20Draft%20Tech%20Manual%20V0-1%20.pdf

3.2.1.5.1.3.2
Self-Assigned Temporary Address of Transmitting Aircraft An “ADDRESS QUALIFIER” value of ONE (binary 001) shall indicate that
  the message is an ADS-B Message from an aircraft, and that the
  “ADDRESS” field holds the transmitting aircraft’s self-assigned
  ownship temporary address.
The self-assigned temporary address shall be generated as follows:
Let:
ADDRP = the ICAO 24-bit address that has been assigned to the aircraft;
ADDRT = the temporary address that is to be generated;
  M(1) = the 12 least significant bits (LSBs) of the ownship “LATITUDE” field (per §3.2.1.5.2.1) at the time the temporary address option is selected;
M(2) = the 12 least significant bits (LSBs) of the ownship “LONGITUDE” field (per §3.2.1.5.2.1) at the time the temporary address option is selected;
M(3) = 4096 × M(1) + M(2);
TIME = the number of seconds that have elapsed since UTC midnight
  at the time the temporary address option is selected, represented as a
  24-bit number.
Also, let “⊕” denote the modulo 2 bit-by-bit addition(or “exclusive OR”) operation.
a. If the transmitting aircraft’s ICAO 24-bit address ADDRP is available, then the temporary address ADDRT shall be the modulo 2, bit-by-bit summation of the permanent address and M(3), that is:
ADDRT = ADDRP ⊕ M(3).
b. If the aircraft’s 24-bit ICAO address ADDRP is not available, then time of day shall be used as an additional randomizer. In that case, the temporary address ADDRT shall be the modulo 2, bit-by-bit summation of TIME and M(3), that is,
ADDRT = TIME ⊕ M(3).

So the question is if this is deterministic.  Could one work their way back to the actual tail number when an aircraft is in anonymous mode?

It is deterministic, meaning that if given exactly the same inputs, it will always produce the same output.
Your second question is whether it is reversible. The algorithm was deliberately designed to require an adversary to know the precise (i.e. within a few meters) latitude and longitude where the algorithm was run to be able to reverse it. This is effectively impossible unless they physically observe your exact startup location, in which case they could presumably just read your tail number off the side of your plane anyway.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Why does TAS increase as altitude increases and why does my C-152 POH seem to contradict this?
I remember learning and memorizing that TAS increases as altitude increases, however I don't understand why. Especially since my C-152's PoH seems to indicate the opposite in the cruise performance section. Can someone please explain what I'm misunderstanding here?

Welcome to Av.SE!

"I remember learning and memorizing that TAS increases as altitude increases, however I don't understand why."-- do you mean when IAS is held constant, or what?  When the throttle position is constant?  When the horsepower output is constant?  In questions like this, it is always important to say what the constraint is, i.e. what variable(s) are being held constant.

. . . and AlexK I think you raised a very good question regarding the POH values of TAS reducing. If something looks wrong, don't wish it away, try and figure it out.

True air speed (TAS) does indeed increase with altitude. The reason is because with increasing altitude the air density decreases. The Indicated air speed (IAS) which is measured by the pitot is a function of the dynamic pressure (Q) acting on the aircraft. The equation for the dynamic pressure is:
Q = 1/2 * rho * V^2
where:
Q = dynamic pressure.
rho = density.
V = True air speed.
According to the equation, if we want to keep the IAS or Q constant in a climb, the TAS should increase, because there is a decrease in density (rho) with altitude. So, there is absolutely nothing wrong with what you have learnt, because it is correct in the sense TAS increases with altitude.
So, why is your POH contradictory. Let us look at it, shall we? I will use the data given at 2000 ft and 12000 ft, under standard temperature to explain what is happening.

If we look at the table we can see that at 2000 ft, if you cruise at 2300 RPM, the engine is able to produce 66 Brake horsepower. The result is a TAS of 96 knots. But at 12000 ft the same engine is only able to produce 54 Brake horsepower at the same 2300 RPM. The reason why the TAS dropped to 92 knots is because your engine is unable to generate enough power at higher altitudes due to the reduced air density (C-152 has a normally aspirated engine). Hence, the aircraft is unable to fly at a higher TAS. If you want to increase your TAS you could increase the RPM to 2450 (more air rammed inside the cylinders) and get a TAS of 100 knots, but that will cost you more fuel.
It is expected that you will climb at the speed for best rate of climb (Vy). Once you reach your cruise altitude, you will push the nose down to level off, pull the power back to the desired RPM and trim it. If you climbed to 12000 ft and set 2300 RPM and trim the aircraft, the IAS that is shown in your air speed indicator will result in the tabled value of 92 knots. The value of IAS is not mentioned in cruise performance is because TAS is what determines your aircraft navigation performance and fuel consumption.

Flying at 12,000’ at 2450 rpm will NOT cost you more fuel because 100 KTAS @ 5 GPH is better than flying at 2000’ at 2300 rpm with only 96 KTAS @ 5.4 GPH.

I was comparing the power at 12000 ft. You burn more at 2450 than at 2300.

Let's remember that the performance chart are the result of extrapolation, interpolation and rounding, likely on a new airplane with a new engine. The climb charts show how rounding can give contradictory results. It generally takes longer to climb the next 1000 feet than the previous. But occasionally, like from 3000 to 4000, it takes less time than the previous 1000. Just because two entries both say "X" doesn't meant they are both EXACTLY the same. Also, the ride up to 12,000 in a flight school's 1980 152 near TBO is going to take a lot more than the 34 minutes and 3.4 gallons predicted.

To the extent that 75% cruise power available is constant with increasing altitude, it's simply that TAS goes up because the constant HP has less and less resistance to work against as the air thins out, while you are able to maintain 75% cruise power by opening throttle more. On a non-turbocharged engine, that is possible up to the point at which the engine is maxed out making cruise power (75%), somewhere around 8000 feet give or take (where the available manifold pressure at wide open throttle drops to about 22").
At this point the engine is wide open throttle just to make 75% power and is maxed out there. As you go above 8000 ft with wide open throttle, by the time you get to 10000 ft it can produce only 68 thrust HP (per the chart, in standard conditions) with wide open throttle and maximum TAS drops to 103 kt.
If the engine had turbocharging, it would be able to maintain 75 HP (75% of 100) to some much higher altitude and you could climb to say, 15000 ft, still making 75 HP in the even thinner air thanks to the turbo, and your TAS would be up to something like, say, 115 kt (you would also need a constant speed prop to exploit that power, but that's another issue).

Imagine that IAS measures the number of air particles hitting your aircraft per second. As you get higher the air is thinner — there are progressively fewer air particles around the higher you go so to get the same number of particles hitting you per second (ergo the same IAS) you need to move faster through the air - your TAS increases.

You have explained the difference between IAS and TAS, but you haven’t explained why TAS is higher at high altitude.

Roger. I added that the air gets thinner as you go up.

With that explanation speed should change with the inverse of density when in fact it changes with the square root of that inverse. I think there is still room for improvement. Hint: The Newtonian impact theory only works for very high Mach numbers.

@PeterKämpf to clarify, at no point did I address the specifics of calculating dynamic pressure with altitude. Pedagogically, I am explaining only in simple terms to try and target the estimated level of understanding required to aid the questioner’s mental model. I have supposed them to be a new or student pilot without the requisite training to jump directly to the maths, if it turns out to be incorrect I apologise for the disservice!

Inflight, the IAS is measured via the pitot/static system and is displayed on your ASI, the primary airspeed display instrument. TAS cannot be directly measured by a probe or transducer, it has to be calculated by using the IAS as a starting reference.
IAS: The pitot pressure is static pressure + the pressure on account of air molecules impinging on the pitot probe from the direction of flight. If the air density reduces, as it does with altitude, in order to fly a given IAS, it requires the airplane to fly faster through the thinner air for the pitot to experience the same pressure and indicate the same IAS. This faster speed is your TAS. Aerodynamic forces such as lift, drag, propeller torque/thrust etc. all depend on the flow of air molecules over the wings and body of the airplane and stall speeds, maneuvering speeds and limit speeds all relate therefore to the IAS.
TAS: is a calculated speed, as there is no instrumentation to physically measure it - in it's simplest form it is arrived at by plugging the IAS into a formula and based on the International Standard Atmosphere. TAS is useful for planning and actual navigation as it is your true speed in relation to the ground in nil winds.
Atmospheric Air Density as per ISA: As per the Standard atmosphere around 6600ft the density of air is about half of what it is at Mean Sea Level, at 12000ft around a quarter, and around 18000ft it is a tenth of the sea level density and so on.
You memorized "TAS increases as altitude increases" but the statement is incomplete in that it gives no info on the reference speed you are flying on your ASI. So a more complete statement is "IAS being constant, TAS increases as altitude increases".
POH 'Contradiction': Your C-152 POH Cruise Performance table seems to indicate a reducing TAS as altitude increases. This is because the page does not indicate the IAS to be flown, instead it gives you an RPM setting for level flight and the resultant TAS (and inflight we accept the resultant IAS). Take 2100rpm, the TAS is:
86KTAS at 2000ft
85KTAS at 4000ft
84KTAS at 6000ft
83KTAS at 8000ft
82KTAS at 10000ft
81KTAS at 12000ft
Seems to reduce with altitude, but calculating the IAS equivalent to the TAS and Alt at ISA using the 'aerotoolbox' webpage gives:
86KTAS at 2000ft = 83KIAS
85KTAS at 4000ft = 80KIAS
84KTAS at 6000ft = 77KIAS
83KTAS at 8000ft = 74KIAS
82KTAS at 10000ft = 71KIAS
81KTAS at 12000ft = 67KIAS

Here are values of TAS for fixed IAS, good for any airplane, and clearly showing the TAS increasing with altitude:
77KIAS
= 79KTAS at 2000ft
= 87KTAS at 8000ft
= 93KTAS at 12000ft

In the cockpit you can either fly a speed on the ASI (adjusting the RPM to suit) or you can fly the manufacturers recommended RPM and accept the resultant speed on the ASI.
As per the POH page, you input altitude and RPM (with mixture leaned) and the table gives you the Power, TAS, and Fuel consumption. The chart gives you this data for an airplane weight of 1670lbs and various RPM settings of the engine at even thousands of feet altitude ranging from 2,000 to 12,000 ft. (And for ISA, ISA-20degC, ISA+20degC.)
An input of altitude - RPM - OAT/ISAdev gives the TAS and fuel consumption per hour. These are the parameters you need alongwith forecast winds to make out a navigation and fuel flight plan. TAS and Wind gives Groundspeed/leg times and Heading to steer, and further with Fuel cons/hr it gives you the fuel for trip etc. The fact that the table outputs no IAS is of no particular disadvantage in the cockpit.
The data could have been shown by using a fixed IAS strategy, replacing the RPM settings with different IAS values in which case you would input altitude, IAS, Temp/dev the chart would output an RPM, TAS and Fuel consumption.

You have explained the difference between IAS and TAS,  but you haven’t explained why TAS is higher at high altitude.

That was already explained by other posts, but i should add it, you're right. 2.  The attempt was to explain why his POH shows lower TAS with higher altitudes which seems to contradict the fact of TAS increasing with altitude. I shall make the answer more explicit. @AlexK may comment if he's read my answer.

Although, it is a backwards way of thinking about it, consider that the True AirSpeed is not changing with altitude for an aircraft keeping a constant speed. In actuality, the Indicated AirSpeed is what is changing. This is due to the IAS being measured by using Ram Air Pressure inside of the pitot tube. The RAP is directly related to the density of the air. The higher the air density, the higher the RAP at the same speed.
More gas molecule mass in the air is entering the pitot at any given time at lower density altitudes (higher air density). Think of it this way. A single bb would have less impact than 100 shot gun pellets fired at the same muzzle velocity.
Your pitot static system is actually measuring the impact of the air molecules and converting that into IAS. In order to fly at a constant IAS at a higher altitude, you have to increase your TAS because the air is less dense (fewer air molecules).

You have explained the difference between IAS and TAS, but you haven’t explained why TAS is higher at high altitude

@MikeSowsun - Because TAS is not higher at higher altitudes. IAS is lower at higher altitudes for the same aircraft speed. But, IAS is measurable with the ASI. Whereas TAS is calculated. Also, IAS is more useful in determining aircraft performance (V speeds, etc). Unfortunately, that is the best way I can explain it. If I can up with something better, I will revisit this.

There is a free lunch. It is the reason airliners cruise at high altitude. The free lunch is LESS drag due to LESS air density which means more speed for the same fuel burn.  The gain in airspeed due to reduced drag magically makes up for less propeller inefficiency.

For a given power setting, True Airspeed increases with altitude because there is less drag due to the air being less dense. Aircraft are more efficient at high altitude because of this simple fact. Providing the engine can produce enough power, any aircraft will fly faster and further, without burning more fuel, if you fly at a higher altitude.
Your C-152 chart shows this quite clearly.
2000’ 59% power = 91 KTAS @ 4.8 GPH
12,000’ 59% power = 97 KTAS @ 4.8 GPH

The air is less dense so the propellor i less efficient and produces less thrust, the wing produces less lift etc.

So there is no "free lunch" here. Take that 150 into space where there is zero air resistance and connect the carb to an air cylinder so it still runs. The prop will turn but produce no thrust so TAS will be zero. At 2000' the prop is turning at 2200 RPM to produce the 91KTAS on 5.4GPH. At 12,000' the prop is turning at 2400 RPM to produce the 97KTAS on 5.4GPH. The engine isn't getting enough air to turn the prop any faster so the only reason the GPH is the same is the mixture is leaned out. Also, since the wing is less efficient with altitude, pitch must be increased so induced drag increases


text:
Why do flight times differ between traveling East versus traveling West?
Why does it take longer to fly East to West than West to East?
Which factors affect this?
Does Earth's spinning affect the time difference? Maybe the air circulation?

prevailing non-tropical winds are westerlies.  Tailwinds flying east, headwinds flying west.

It has nothing to do with the rotation of the earth, since the atmosphere rotates with it.

@DavidRicherby Actually, the jet streams are caused (indirectly) by the rotation of the earth.

To add a little more "concreteness" to the question, many ocean crossings use tracks (routes) defined on a daily basis.  The forecast wind is a major factor in defining these routes so that east bound traffic can take advantage of the winds aloft westerlies and west bounds can minimise the impact of head winds.  See here for examples - https://pilotweb.nas.faa.gov/common/nat.html and here http://en.wikipedia.org/wiki/North_Atlantic_Tracks

@DavidRicherby Here is a seven year late comment: The prevailing winds are affected by the rotation of the Earth via the Coriolis effect. See my answer below.

As Robbie's answer implies, the answer is wind - Trade Winds govern what happens on or near the surface and were historically important for sailing ships, and today in aviation we deal with the the Winds Aloft at whatever altitude your plane is flying.
As an example, consider two hypothetical flights at 30,000 feet with the winds shown below:

With these winds a flight from A to B (East-to-West) will be fighting headwinds the whole way. My handy flight planning program tells me that at 500 knots (airspeed) you'd be in the air for about 5 hours 30 minutes.
Traveling in the opposite direction from B to A you'd have a tailwind, and with the same 500 knot airspeed you would make the trip in roughly 4 hours.

The winds aloft vary seasonally, which can affect flight times for summer versus winter trips. According to one of our folks who is regularly up at those altitudes even the daily variations can be noticeable, and may make the difference between being able to make a nonstop trip or having to stop for fuel on the way.
Pilots and flight dispatchers will often review the wind data prior to flight and try to select an altitude that affords a "good ride" (free of turbulence) and favorable winds (either a tailwind or the lowest headwind they can find).

"My handy flight planning program" - right, because you're a pilot, so you just have one of those lying around. I wonder if laymen browsing the other StackExchange sites feel like this when someone busts out a boolean satisfiability solver or a 270-dollar official copy of the C11 standard.

@user2357112 "handy flight planning program" as opposed to "Taking out a pen and paper and figuring out where the wind speed/direction changes, how long I'll be flying with each wind component, and what effect that will have on my ground speed" - Anyone who has taken High School physics can do the math (it's vector addition), but nobody wants to :-)

@user2357112 you can also find those "handy flight planning programs" online for free! Here is one example but there are many more: https://www.fltplan.com/AwMPToQuickInfoEntry.exe?a=1  This one will give you the differences in travel time based on different headwinds or tailwinds. :)

Hi @voretaq7:  Its a good answer. But I have a small question. Lets consider the following question. When u r travelling against the air by some 500knts, ur speed is eventually reduced because of the barrier. But this will not be the case when, the air is tailgating u. This tailgating air will add some extra cruising speed even when pilot is not increasing the speed right ?  But travelling in the opposite side of the air can be satisfied by increasing the cruise speed when he want to reach in the same 4 hrs. Right.. ?

@NANDAKUMAR Airlines plan flights to cruise at roughly the same fuel-efficient airspeed regardless of winds. The difference in flight times is therefore due to the movement of the air over the ground, i.e. wind. Even if planes had sufficient reserve thrust to negate a headwind (and they don't), the increase in fuel cost would be prohibitive.

The Trade Winds do not make westbound air travel slower, the Westerlies do and they appear between 30-60deg latitude as shown on your picture. The Trade Winds are closer to the Equator.

Seven years late!) but all the answers that say "wind" attribute speed difference to the "trade winds" which are the wrong prevailing winds to name as they act in opposition to OP's "westward flight is slower" premise, which is also only true at certain latitudes. None of these answers even mentions the effect of Earth's rotation, though specifically asked by the OP. Both the prevailing winds and the jet stream affect duration of East or Westbound air travel, and both depend on differential heating and the rotation of the Earth to determine their direction and speed.
Prevailing Winds
This diagram shows the macro air circulation patterns around the globe. Generally, air is heated at the equator and rises, then travels at high altitude towards the poles. At about 30deg latitude the air mass has cooled sufficiently that it wants to descend, then heads at low altitudes back towards the equator. This is the Hadley cell. From space, these airflows appear largely Northerly and Southerly. On Earth, the Coriolis effect makes the airflow also appear Easterly and the result is called the Trade Winds. Here, westbound air travel is faster than eastbound.

Similarly, air is cooled at the poles and descends, then travels at low altitude toward the equator to approximately 60deg latitude where warming makes the air rise. This is the Polar cell. The same low altitude direction toward the equator and the same Coriolis effect makes these wind directions match the Trades, and they are called the Easterlies.
Polar and Hadley are driven by polar cold and equatorial heat. If the Earth were smaller they would combine into one cell. At the existing scale an intermediate cell forms, the Ferrel cell, and its direction is driven by contact with Polar and Hadley at 30deg and 60deg.
Polar makes a "chimney" at 60deg which is shown on the chart as low pressure. Hadley makes a downdraft at 30deg, shown as high pressure. The Ferrel air mass flows from high pressure to low, or toward the poles at low altitude. With airflow reversed the Coriolis effect now makes the winds appear westerly, and are aptly called the Westerlies. This is where air travel in the US and Europe occurs, and this is where the OP's "westbound travel is slower" applies.
Jet Stream
This phenomena occurs in addition to the prevailing winds and is affected by the same factors. There are usually four jet streams, one located near each of the vertical air flows between the circulation cells. The 60deg latitude Polar jet streams are stronger and lower than the 30deg Subtropical streams, and this explanation focuses on the northern Polar jet.
From this diagram you can see circulation in the norther Polar Jet. Looking Eastward in the direction of the jet stream airflow there is a counter-clockwise rotation between the Ferrel and Polar cells. Though this entire column of air is ascending, the temperature differential between the colder air of the Polar cell and the warmer Ferrel air causes this weak rotation. Location and altitude fluctuate, but the lower reaches are around 30-40kft where transport aircraft fly.

You might think that the lower altitude flow toward the equator would combine with the Coriolis effect to create a mild easterly flow as happens in the Polar easterlies. It does attempt this but runs into the much stronger Westerlies and is deflected, accelerating as it moves in a westerly direction. Think wind blowing into a wall, deflected to move along its length. Depending on local temperatures, the deflected air can reach speeds as high as 200kt.
So both atmospheric heating/cooling and the Earth's rotation via the Coriolis effect determine the direction of the prevailing winds, and consequently the amount of time air travel takes in a particular direction.

Really, really nice answer!

@RalphJ I added jet stream effect.

I'd upvote again for that addition if I could; really appreciate the detail & the clarity in this answer.

@RalphJ Nice bounty!

It'll be a day or two before the system lets me  award it, but since there is no second up-vote available, it's a nice alternative.

The jet stream moves from West to East. At the altitude an airliner flies the speed of the tail wind or head wind will have a significant impact on actual ground speed. This was first observed when B-29 bombing raids on Japan during WW2. Before that there was no notion of a 'jet stream'.

Actually, the Japanese were aware of the jet stream already in the 1920s. They used it during WWII to send balloon bombs across the Pacific to the US: some of these made it as far as the Mid-West.

They never understood it the way it is understood today, although, yes, they did take advantage of it. They never once knew that it was a global phenomena.

Well, obviously, knowledge has improved in the 90 years since then... But the Japanese understood in the 1920s that there are consistent, strong winds from west to east across the Pacific at the latitude of Japan so it's not true to say that the first observation of the jet stream was by Americans in the 1940s.

Short answer: As you have indicated in the question description, the answer is winds. Better known as Jet Streams.
Long answer: https://alliknowaviation.home.blog/2019/03/29/why-do-planes-travel-faster-west-to-east/

It's not just jet streams, it's the Earth's prevailing wind patterns. supposing a headwind component of 24kts on a 10 hour westbound flight

Sorry, incomplete comment above: It's not just jet streams, it's the Earth's prevailing wind patterns. supposing a headwind component of a modest  24kts on a 10 hour westbound flight - that's 24nm more travelled per hour which is 240nm in 10 hours. Cruise TAS of 480 kts ~ 8nm per minute so 240nm means a difference of 240/8 = 30 minutes more than in 0 wind conditions (aka still air). If the return trip has a tailwind component of 24kts, anticipating a 9 hr flight works out to 24 x 9 =  216nm so 216/8 = 27 min less. These 2 approximations add up to 30 + 27 = 57 min between the Wbound and Ebound.

Although the rotation of the earth and weather created by solar energy do affect the air circulation of the planet, and jet streams aloft, the main reason why west to east flights take "longer" is that flying east into new time zones adds an hour to your landing time for each time zone flown through.  Opposite flying west.
Some of this is made up for when flying at the latitudes of west to east jet streams when travelling east, so the actual flight time going east under those conditions will be shorter,
even though you arrive at a "later" time.
A closer look at your flight time based on your original time zone may give greater insight
to your question, and maybe a little less "jet lag".

Both the winds and earth's rotation affect the difficulty of flight eastbound vs. westbound.  If eastbound is slower and harder and winds carry you westbound, I take it you're within the tropics, where the tradewinds govern flight direction.  Kentucky and Utah, and farther north latitude (and likewise south to Argentina) the winds work in the opposite direction.
The poles and equator differ in (eastward) rotation speed.  The equator has farther to go and keeps up with the axis by going faster.  So land nearer the axis (Canada, Argentina) takes it slow spinning east, slower than wind and weather.  So that's where to take advantage of the winds eastbound.  The tradewinds are at the equator, where the ground follows (east) a bigger circle, faster than wind and weather.  There, the westbound is more efficient.
I'm not sure about Alabama/Arizona/etc, but I wager the eastbound and westbound are about the same, since they are in-between the north and tropics (and Bolivia the in-between of the southern hemisphere).  The latitude makes quite a difference.
Unlike planes being pushed by wind, space shuttles leave the atmosphere.  Being propelled only by earth's rotation, all rockets go east no matter the latitude.

I'm finding this a bit confusing to follow... are you saying that rotation affects flight time apart from the wind?

Unlike planes being pushed by wind that's valid only if it is a tailwind

@Federico well a plane could be pushed in any direction.

@fooot he's using it in the sense of "push forward", see the propelled a few words later.

While this answer is correct about the direction prevailing winds blow, it's completely off about the reason. The actual reasons are quite a bit more complicated than this and have to do primarily with global heating patterns. Long story short, there's a persistent cyclone at each pole (which is stronger in that pole's respective winter season.) The jet streams we usually refer to are the polar jet streams which occur between the mid-latitudes and the polar vortices. There's a weaker jet stream between the tropics and each mid-latitude zone, but they're too high to be useful for most flights.

Without even looking at the winds I'd just add something like 20 kts ground speed if going east and subtract 20 kts ground speed if going west. Amazing how often that came close enough to actual flight plan.

"winds ... add to ground speed going east" A quite practical answer. And it was a reliable heuristic when I did flight planning flying out of Texas.  How does this not answer the question? More to the point, how is it wrong? Down voting is not about "liking" an answer. It's about correctness. If not the best answer then don't vote for it. But it's not wrong. And, if it is wrong then down voting w/out saying why is a dis-service to everyone who comes here for answers.

I did not down vote your answer, however I can see why some people would. The question is why do flight times differ, and you did not answer that question.  While your answer is interesting and potentially useful (depending on the type of aircraft being flown), it does not answer the question that was asked (see [answer] for more details).  This would be better suited as a comment than an answer.

Well "the answer is wind." quoting above.  But no one mentioned Matthew Fontaine Maury, what answer can be complete without starting with this guy? We can go on to how bombing Japan in the world war lead to the discovery of the jet stream.  Your point about comment vs answer is well taken.

Right, and your answer does not say that the cause is the winds (although it makes one reference to it).  How it was discovered isn't required in order to describe the physical phenomenon though.  ;-)  At any rate, I'm simply trying to offer a suggestion on how you can improve the answer since it hasn't been well received by the community.

don't get me wrong. This answer may be succinct but it is not insightful;  winds? duh. My point is about down voting not the answer itself, which really blows.

I downvoted, because it includes no details that would make the answer useful. For example, it makes a huge difference whether you were an airline pilot doing cross-Atlantic routes or a GA pilot in that one valley where certain winds prevailed. Secondly, you don't address why you added those 20kts; was it because of wind, orbital effects, UFO interference, magnetic fields? Of course, you know it is the winds, but your answer doesn't actually say that. I'd happily upvote a more detailed version of this answer even though it doesn't answer the question exactly.

Note that downvoting is not reserved for when the post contains wrong information, but also when it's "poorly researched, or fails to communicate information." Also, please don't take my downvote as an attack on you, your willingness to help others or your capability as a pilot, but solely because I didn't think the answer was helpful at all without the details I mentioned in the last comment. I'm genuinely sorry if my negative feedback made you feel that way.

please don't take my downvote as an attack on you Absolutely not. If anything requires attention to detail it's flying. But then we "measure with a micrometer and cut it with an axe."

It is simple. The Earth rotates from East to West. There is hence an eastward shear effect in the atmosphere. If you fly East, this shear adds to the cruising speed. Reverse case if you fly west. So more time if you fly westwards. But how much more depends on the prevailing wind-shear. This cannot be pre-determined except when you actually fly and meter the wind speed.

Also, the question was actually for the opposite effect (prevailing winds are not in the same direction at all latitudes, so the Earth-rotation cause is quite indirect).

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Is this a sunken plane?
I encountered this in Google Maps satellite mode about 3 weeks ago. I thought it may be a passing plane and it goes away when the images update. But now after 3 weeks it is still there. The existence of the shadow also made me think it's a passing plane. But the other characteristics made be doubt about it:
There is a huge black color between the tail and rest of the plane. It looks like a severe fracture. Also, one of its wings looks fractured from top to bottom near the tip. The other wing looks partially fractured near the tip.
It seems that the lines of little waves on the surface of the water are above the plane (hence it seems the plane is below the water).
Is this a sunken plane or a passing plane?
Overview image:

Detail image:

The coordinates: N 27.144986°, E 56.461160°.
Google Maps link

I can't answer with certainty, but it's likely just an illusion due to the rather complex image processing, stitching and compositing that is done on satellite imagery. Notice the colored halo of the same shape to the northeast. Real objects below the water's surface are rarely visible from above, and almost never with that level of detail. It's much more likely a plane in the air that is distorted by the image processing.

@TypeIA I also have found a seemingly drowned vessel near the plane at the following coordinates: N 27.128059°, E 56.220373°.

Great finds! I still think both are simply artifacts. See this article for a more detailed "debunking" of a similar apparently "sunken" plane.

Lake Harriet is still mysterious! Now I found ghosted vessels besides obvious ones in the WNW of it.

@TypeIA Can the plane also be identified?

@SnackExchange My best guess would be a Learjet, maybe a 40 or 45. Distinctive features being the T tail, engine placement and the lack of swept wings. https://www.skybrary.aero/sites/default/files/LJ40_3D.jpg but it's only a best guess.

Not a Learjet. More like a older twinjet Falcon or a Citation.

@TypeIA I think it's too big for a Learjet. My guess is it's a Fokker 100, a type that is still used by a few airlines in Iran.

@DeltaLima The data I get from measuring it in Google Earth shows a length of about 116 feet and a wingspan of 92 feet, which lines up with the Fokker 100.

@TypeIA I think the artifact I experienced is the cleanest artifact ever! The artifact of Lake Harriet for example was so blurry and bad-colored.

Similar answer, but clearly a different question. Don't trust Google Maps, except for shopping.

This is definitely an artifact of image processing, not a sunken plane. The red, green, and blue planes just in front of it are a dead giveaway- this results from three different exposures being taken with three color filters on a fast-moving object. Since the airplane has moved slightly between exposures, the composite of these three images results in an artifact like this rather than a single plane.
Also, I'm not sure of the exact aircraft type, but planes that look like that (e.g. a Learjet or Citation) are on order 15 feet tall. Glancing at a nautical chart, the water is not even 15 feet deep there. So not only would it be sticking out of the water, there's basically no chance it would not have been discovered and salvaged pretty quickly.


text:
Why is airflow forced to be speed up on the upper surface of an aerofoil?
As the title says: Why is airflow compelled to flow further over the upper surface of an aerofoil? I understand because it has a larger distance to travel, but why can't the airflow travel at the same speed as the airflow underneath the lower surface?
I understand how the Bernoulli effect works but there is no constriction in an aerofoil, why does it speed up with the Bernoulli effect; without the constriction?
I also understand that the there is a wrong theory that airflow over the top of the wing wants to meet the airflow on the lower surface at the end of the aerofoil, at the same time.

@GregHewgill No that just explained how lift is generated. Although it did mention the concept of the wrong theory, it did not explain why it needs to travel faster

It does say that air has to have a lower pressure to negotiate the curved, inclined upper surface. Bernoulli (and that answer) tells you that lower pressure equals higher speed and the suction causes air flowing towards it to accelerate. So what is missing?

Airflow isn't compelled to do that by some edict.  It just does it.  "Why" isn't all that meaningful, compared to a theory or formula with predictive power.
Bernoulli says that, under certain conditions, a fluid's speed and pressure have a certain relationship.
How a fluid flows past a obstruction, and what net forces and torques it exerts on that obstruction, aren't because of Bernoulli.
The closest we can come to a reason for the fluid's behavior is the Navier-Stokes equations.  But that's still a model, a simplification.

For an airfoil in conventional steady flight, it's actually more useful to say the reverse:  because the airfoil has been carefully chosen to generate lift under those conditions, the pressure above must be less than that below, so Bernoulli predicts that the flow above must be faster than that below.  And we can confirm that with CFD simulations or with onboard sensors.

That is an answer worthy of Philosophy SE. +1!

it is because of the camber provided on the upper surface.the area where flow can move is decreased due to pronounced camber.and according to equation of continuity the velocity will have to be increased to maintain the same airflow


text:
Can an LLC formed solely to own and operate an aircraft be operated under Part 91?
A non-pilot purchases an aircraft and puts it into an LLC. Then non-pilot hires pilots, places insurances, rents a hangar and pays for all other costs and expenses with the sole purpose to fly the his family on personal trips and vacations (no business purpose), can the aircraft still be operated under Part 91? Or, because the non-pilot who owns the LLC is providing funding for the operation of the aircraft, does this constitute operations under Part 135?

Welcome to AviationStackExchange. Part 91 air operations are not restricted to non-commercial flights, personal flights, or flights without compensation. Could you include the section of 14 CFR Part 91 that leads you to believe that?

My question was whether the AIrcraft can be operated under Part 91 under this factual scenario.

My concern is whether by the LLC owner funding all costs of the aircraft, that would constitute compensation for hire thereby converting the aircraft to Part 135

Part 91 does not prohibit commercial operation of an aircraft. It does not matter if the aircraft is owned/operated by an individual or an entity. Part 91 does not prohibit compensation for hire. Part 135 does require a Part 119 certificate from what I can tell from the regs. And, a Part 119 certificate is not required when common carriage is not involved in aircraft of less than 20 passengers or 6k lbs payload. In other words, the owner, operator, and/or pilot can not hold themselves out as a carrier of the general public to the general public. They are strictly for private carriage.

I was looking at Sect. 91.501(a) which states as follows:

(a) This subpart prescribes operating rules, in addition to those prescribed in other subparts of this part, governing the operation of .. turbojet-powered multiengine civil airplanes of U.S. registry...
(b) Operations that may be conducted under the rules in this subpart... include -
(4) Flights conducted by the operator of an airplane for his personal transportation, or the transportation of his guests when no charge, assessment, or fee is made for the transportation

I would suggested you edit your title question to be phrased as a question.  (No need to shout either...)
Also, what does "compensation for hire" actually mean?

Review FAA AC 120-12A. It gives you guidelines for defining private versus common carriage. The owner of the LLC is what this part specifically relates to. They can fly as many family members, friends, company officials, etc., as guests as they choose. However, they can not change those guests for the flight. This would be considered operating as an air carrier or “holding out”.

I guess the question is whether an LLC formed solely to own and operate an aircraft can be operated under Part 91.

I can not point to specific numbers or sources for numbers. Anecdotally, I can say that most aircraft that I know of are owned by an LLC formed solely to own and operate an aircraft. Every Cessna, Piper, Robinson, etc., that I have flown were owned by an LLC or other corporate structure. Sometimes, those LLCs were owned again by other corporations. This is quite common in aircraft rental, flight schools, flying clubs, leasebacks, and fractional ownership. For the most part, they are all flown under Part 91. It is done for liability purposes. And, I meant charge, not change, earlier.

That's what I have seen also.

Does this answer your question? Can a commercial pilot fly passengers for hire without an air carrier certificate?

Does this answer your question? What do the terms 'holding out' and 'common carriage' mean?

Your scenario is basically the same as any Part 91 corporate flying. There are several answers on this site already that explain why it's "holding out" and "common carriage" that determine whether a flight requires compliance with something other than Part 91 rules, and not simply who's paying for the flight. See proposed duplicates. If you think your question is still unanswered, you need to explain how the existing answers don't address what you're asking.

Would everyone who is arguing about private vs common carriage please review FAR 119.23(b). Private vs common carriage is not what determines Part 91 vs Part 135. What determines that difference is 119.1: "This part applies to each person operating or intending to operate civil aircraft as an air carrier or commercial operator, or both, in air commerce..." The proposed operation is not an air carrier or commercial operation (as long as family is not paying for the flight). Since it does not fall into the applicability requirements of Part 119, this flight can be made under Part 91.

Nobody has suggested this might be common carriage...

In order to find out whether a particular operation requires an operating certificate or an air carrier certificate (and thus must conform to Part 135 or 121 or etc), you have to look at Part 119, which describes all the operations that need to be conducted under those Parts. So let's take a look at FAR 119.1:

This part applies to each person operating or intending to operate civil aircraft - (1) As an air carrier or commercial operator, or both, in air commerce; or... [yada yada large airplanes]

Let's assume that you don't mean a large airplane for the purposes of this discussion. If you do mean a large airplane, flown privately by the single owner, then the flight must be under Part 125.
If you mean a small airplane, then Part 119 would only apply if the aircraft were operated as "an air carrier or commercial operator" So the question becomes whether a private entity (being an LLC has no bearing on these questions; it might as well just be Bob the airplane owner) can hire a pilot and not be an air carrier. The practical answer is that that happens all the time under Part 91. Corporate aircraft with hired pilots fly under Part 91 regularly. They are able to do this because when an entity like Bob or the LLC or the corporation flies their own airplane, then they are not acting as air carriers or commercial operators.
The definitions of these things are in FAR 1.1:

Commercial operator means a person who, for compensation or hire, engages in the carriage by aircraft in air commerce of persons or property, other than as an air carrier or foreign air carrier or under the authority of Part 375 of this title. Where it is doubtful that an operation is for “compensation or hire”, the test applied is whether the carriage by air is merely incidental to the person's other business or is, in itself, a major enterprise for profit.

Bob, LLC is clearly not a commercial operator because Bob, LLC is not carrying persons or property for hire. Bob, LLC is engaged in private flights for the benefit of its owner(s) and is not a major enterprise for profit. Nor is Bob, LLC an "air carrier." An air carrier is all those things a commercial operator is, and operates interstate routes. Again, the definitions are in Section 1.1, but you have to root around a bit to really get to the heart of the question.
As an aside, most commercial operations are air carriers. But because Federalism, Part 119 has to formally treat interstate and intrastate commerce differently. That is why there is a difference between "air carrier" (which is interstate commerce) and "commercial operator" (which is intrastate commerce).
Since the LLC does not act as an air carrier or commercial operator, Part 119 doesn't apply to it and it can operate Part 91.
All this noise about "private" vs "common" carriage is a red herring. Part 119 applies to both. The only difference it makes is whether you have to look at 119.21 or 119.23 to determine what kind of certificate you need and which part of the FARs (135 or 121) you must comply with. ...IF you're a commercial operator, which your LLC is not.

Excellent answer, and I didn't see it before I added to my comments below.  So, don't feel the need to respond to my comments directly, yet...  But, I will have some questions for you:  First, I quoted the definition of Air Carrier below, and is says nothing about interstate, major, or for profit.  I agree that Bob the LLC doesn't meet our typical image of an air carrier, but he certainly meets this definition, right?  As a person engaging in air transportation?  (I guess if you want to get silly a student pilot renting a 150 for a solo also falls under this extremely vague definition...)

Second question, you make a point that Bob the LLC is not a commercial operator because he isn't carrying people for hire.  However, the commercial pilot he hires is definitely a "person, who for compensation" is carrying people.  Why does this fact not make the operation commercial?  It makes no distinction between who owns the aircraft...

The short answer is yes, an aircraft owner can hire a pilot to fly him or her, as well as other friends and family, and operate under Part 91.  This is called private carriage, as opposed to common carriage.
Just to clarify a few points:

The pilot hired would need to have a Commercial Pilot Certificate, even if no money changes hands, because the FAA considers flight time as compensation.
The owner could not charge other passengers because this would constitute common carriage, (operating as a charter) and require a Part 135 Operating Certificate.
It makes no difference whether the owner is a rated pilot or not.  Some owners fly themselves, but want the security of having a more experienced pilot along with them.

P.S.  I realized looking related questions on the right side that this is pretty much a duplicate of this question:  Can an aircraft operator hire a Commercial Pilot to fly their aircraft under part 91?

Your answer is correct for the wrong reasons. The proposed operation is not "private carriage." Private carriage is when a commercial operator does not hold out to the public, and instead only flies under contract with one or two clients. This situation is not that; this situation is an aircraft owner arranging to have someone fly himself and his own family in his own plane. It is not a commercial operation and not covered by Part 119. It is clearly a Part 91 operation.
If it had genuinely been a private carriage operation, that would still be Part 135. See FAR 119.23.

@Dave-CFII, I appreciate the feedback, but if a contract is in play and money is changing hands between an owner/operator and a commercially rated pilot, then it is most definitely a commercial endeavor. And since it is obviously not common carriage, it is, by default, private carriage.  I stand by my answer that this deal would constitute commercial private carriage, and I never stated that it fell under part 119.

P.S. according to an article I found on Avweb.com: "Private Carriage for Hire is any business-related flying for hire that does not involve advertising or holding out to the public. It is done under special exceptions to the general operating rules of Part 91."  That mirrors my answer...

Avweb is a great resource, but the FAR is better. FAR 110.1 defines: "Noncommon carriage means an aircraft operation for compensation or hire that does not involve a holding out to others" ("private carriage" and "noncommon carriage" are always found together in the FAR). It does NOT define noncommon carriage as "any business-related flying." It is defined as a certain kind of operation for hire, and the OP's situation is not an operation for hire. Merely hiring a pilot does not make an operation an operation for hire, no. See definitions of "air carrier" and "commercial operation" in FAR 1.1.

@Dave-CFII, your comments are not making much sense. Paying a commercial pilot is not commercial? Hiring someone is not for hire? “An aircraft operation for compensation” is non-common, or private carriage, but this aircraft operation, with this pilot being compensated, is an exception because _____ (the LLC owner is a passenger?). Please justify your points with logic statements and don’t simply tell me to read the FARs.

And if you have a specific section that bolsters your case, please quote it directly and provide your interpretation. The quote you provided above  110.1does not contradict any of my points, it simply reinforces that this is not common carriage. Which is not in dispute. In fact, it furthers my point: If non-common carriage is synonymous with private carriage, and is defined as an aircraft operation for compensation, (which this is) that does not involve holding out, (which this doesn’t) then this is private carriage. Follow my if/then logic flow?!

And since you mentioned it, from 14 CFR 1.1 definitions:  "Air Carrier means a person who undertakes directly by lease, or other arrangement, to engage in air transportation."  The LLC owner in this example would meet the definition of an air carrier.  In case your point was that he/she does not...

P.S.  Just in case it needs to be said, I value truth above all.  I have a very small ego, and if you can prove me wrong I will gladly concede and change my tune.  We are all here to learn.  I just think you are applying a narrow interpretation of broader terms in a context you are most familiar with, and I am try you to challenge you to think outside that box.  Because if this isn't commercial private carriage, and it isn't pro-rata cost sharing under a PPL, then what is it?!


text:
How deliberately stall fixed wing reduce drag if stall decrease static pressue?
In this VIDEO at 5:40 we can see how stall decrease pressure at upper wing surface.
If stall/flow separation reduce static pressure how in this VIDEO they reduce drag when stalling the wing?
Here is description how works:
https://formula1techandart.wordpress.com/2010/12/14/mc-laren%E2%80%99s-innovative-rear-wing-system-f-duct/
https://www.formula1-dictionary.net/f_duct.html

I don't know about pressure, but stalling always increases drag.

This is not about aviation, voting to close.

Concepts are related to "blown flaps".  Let's work to understand it.

@RobertDiGiovanni, then edit the question and graphics to be about blown flaps on airplanes.  This site is about aviation, not automobiles.  (Race cars have tires, should we allow questions about race car tires because airplanes also have tires?)  You don't have to agree with me, but the vote stands.

@MichaelHall I see your point and respect your verdict, however, I find this question interesting as an aerodynamic optimization task. Also, I wonder whether a car site will be able to answer it well.

@PeterKämpf, and I agree with what you just said...  But, I believe Jurgen has a responsibility to establish a connection with aviation in order to make it relevant enough to keep open.

@MichaelHall I think question is great, it shows the beauty of aerodynamics at its best. Aerodynamics is basics of aviation and this question is 100%  about aerodynamics.

@JurgenM Aerodynamics is at the basics of aviation, but that does not mean that every aerodynamics question is fit for this site. Since this question is about a stalling airfoil, the aerodynamics could fit into the domain of aviation and be of interest to our community, but it is borderline.

Questions about aerodynamics are off-topic here, unless they are related to aviation. As currently written, this question is exclusively about F1 technology. Why not rephrase it to something like Could this F1 technology be used to reduce drag on aeroplanes?

As the linked site explains, this is not about aerodynamic drag of the flap but the whole drag of the vehicle.
F1 cars use rear wings to increase downforce so they can turn faster. The downforce of those wings increases the load on the tires and, consequently, the amount of side force they can tolerate before they skid. This allows to drive faster through turns.
This tire load, however, increases rolling resistance, so on straights it would be better to do without this downforce. In airplanes we use moveable flaps but the F1 cars have decided to vary flap lift by blowing air into the low-pressure side. This raises local pressure, reduces downforce and, consequently, rolling resistance so the car can drive faster.
In effect, by switching the air flow on in straights and blocking it in turns, the car can be optimized to both run faster on straights and run faster in turns without skidding.
Since the low-pressure side of the wing and flap is pointing backwards, increasing local pressure also should reduce the amount of aerodynamic drag there. But the main effect is to vary the lift this wing and flap produce and thus to vary downforce such that the car can reach higher speeds overall.
Stall in aeroplanes means drag goes up because lift needs to be produced and stalling makes this less efficient. Here, however, stall will greatly reduce lift - in cars there is no need to keep lift equal to weight! And reducing lift will also reduce drag, even though the L/D ratio might go down in the process.

If you close the slot between main wing and "flap wing",all rear wing will stall. Will you then increase drag and will you increase lift of rear wing compare when slot is open and flow is attached?

@JurgenM closing the slat will greatly increase drag and decrease downforce. While blowing into the low suction area reduces downforce, too, it causes drag to increase less because the additional air volume will raise pressure in the separated flow. Closing the slot is less helpful than blowing.

" While blowing into the low suction area reduces downforce, too, it causes drag to increase less "  You write in your answer that blowing air in low pressure side reduce aero drag of wing, not increase. ?

@JurgenM … relative to separation without blowing.

So when f duct is ON(blowing) aero drag of wing is lower then when f duct is OFF(attached flow)?

Yes, aero drag and rolling drag are lower, and so is downforce. Only the L/D of the wing is lower, so drag goes down less than downforce. Still better for speed than with blowing off.

"Typically, wing stall is correlated with an increase in aerodynamic drag force. However, in the case of the finite wing with low aspect ratio, the induced drag is dominant and is proportional to the downforce. Therefore, flow separation on the wing increases the profile drag while simultaneously reducing the induced drag, resulting in a decrease in the total aerodynamic drag."  https://journals.pan.pl/Content/84720/PDF/03_paper.pdf  stalled wing has lower drag even in case with just slot  closed...dont agree?

@user628075 Why shouldn't I agree? I still think that blowing air into the highest suction is more efficient, but closing the slot will also reduce lift.

yes blowing air is more effective then close the slot, but you write in comments that close the slot will increase drag..."before blowing teams used flexible wing sections which allowed the 'slot gap' to close up under high aerodynamic loads and stall the wing. Once this became evident to the governing bodies it was rapidly outlawed. Wings are now subject to static load tests to ensure that they cannot flex.
So if a team were able to achieve a similar effect within the regulations, considerable straight-line performance gains could be made."

This is more race car - technical, but in this reference they explain that only the rear slotted portion of the airfoil is stalled, not the entire  (inverted) wing.
Apparently, the reduction in downforce in straightaway results in an increase in speed.  This may be due to a variety of factors, such as the rear tires being "squished" or compressed less, reducing their friction and energy loss from deformation.
The claim is that the lift to drag ratio is reduced, but lift is reduced so much more that there is a net loss in drag.  This explanation may be somewhat dubious but apparently the device works.
A more suitable reason may be that the flap is angled in such a way that it's "lift" not only produces downward force, but also a significant amount of rearward force. When the "bleed slots" are activated by the driver, they simply reduce the flap lift without stalling it.

,some teams blown air in main wing, some in second wing


text:
Where does the APU draw its intake air?
In an airliner, where does the APU draw its intake air?
Is it a similar location for all airliners, or do different options exist?

The APU is usually located at the rear of the aircraft, in the tail, so the intake is generally somewhere on the side of this location. Aircraft place the inlet in different places though, and some even put the APU somewhere different. For some examples:

737 intake, the small NACA inlet at the bottom
E145 (the place they don't want you to put de-icing fluid)
B777 (the scoop that opens upwards)
A330 (a scoop on the underside of the tail)
B727 (inside of the wheel well)
Here is an interesting thread including other examples.

The Boeing 737NG APU inlet is on the right side of the tail cone and the exhaust is
Through the tail.

The specific location varies a bit with each aircraft, but in general, they are located close to the APU - so in the tail.
Many aircraft will have a door on the top of the fuselage that opens when the APU is running, while others have an inlet that is always open, like on the 737.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Feasibility and process for the approval of a modified glider
I am looking into a business idea that requires glider sized semi-automatic drones but I am very naive when it comes to the regulations and rigour of the aviation and airline industry, so I am hoping I can find some help here. As I understand it, introduction of a new aircraft into the market requires testing all components of the aircraft extensively and after a few test runs, if it is considered safe, it's given a type certificate. This process can take anywhere from 5 to 9 years. However, I am wondering if it is possible to make it cheaper or faster if only modifications are made to an already type certified aircraft.
Assume I got my hands on a glider and manage to add a small gasoline\jet-A1 motor to it (or maybe directly purchase one with a motor), and modify it so that it can be operated remotely with minimal guidance. How likely is it that such an experimental aircraft is going to be approved?
When I say semi-automatic or with minimal guidance, I mean that the aircraft can fly by itself given a flight path (similar to an auto-pilot) and human assistance is needed only when landing - since there needs to be constant communication between the control tower and the pilot- or if the air traffic control requires the pilot to alter the flight path for some reason. The remote pilot would ideally be overseeing around 5-10 of these drones at the same time. Is such a modification to a glider possible given the current laws and regulations?
These gliders would be flying to small airport rather than the ones like newark-liberty so they would not cause to much trouble to commerial air traffic. Finally, what is the procedure, cost, and time needed to use such a modified aircraft for commercial applications?
Edit: This question has been closed for being too broad,although I believe it is not. In essence, I am asking for what the procedure is to bring an experimental aircraft to market, and how likely it is. These two questions can be answered in a single answer. If the community still finds this too broad, please suggest changes so I can narrow it down.

In the olden days, "Too broad" meant that an entire chapter, or entire book, would be needed to answer the question appropriately and thus wasnt a good fit for a Q/A site. Entire volumes of books could be written on the subject of bringing an experimental semi-UAV to fruition. This question is massively too broad.

In addition, How likely is it that such an experimental aircraft is going to be approved? would be opinion based at best. Is such a modification to a glider possible given the current laws and regulations? raises more questions than could be answered and Finally, what is the procedure, cost, and time needed to use such a modified aircraft for commercial applications? is like asking how long is a piece of string. So you're asking multiple questions, none of which can be answered in any reasonable sense. Now do you understand what "Need's more focus" is alluding to?

VtLC: Sorry, but you've not reduced the number of separate questions at all. You ask three questions. Yes, while they are all tangentially related to the creation of an experimental airframe, they are each way too broad. Please read Jamiec's comments and heed them. How on earth would we be able to produce a cost basis to do what you desire? And that is cherry picking a single portion of a single question.

The certification process for the airworthiness of a type design in Europe is rather straightforward, regardless if it is a new design or a modification of an existing one:

You establish a design bureau and apply for recognition as an Approved Design Organisation (DO) according to EASA Part 21 Subpart J. This requires to have specialists on hand for all aspects of airplane design, including fringe disciplines like lightning protection.
Once your design has progressed far enough, you apply for a type certificate with your local authorities. Essential for a successful certification project is the exact definition of the type design at an early phase of the project. The type design should include drawings and specifications but also information on materials and processes, including methods of manufacture and assembly of the product
You compile a Means of Compliance (MoC) list which covers how each individual article of the regulations will be fulfilled. The means could be either the use of a proven design (like an already certified system component, manufacturing procedure or material), analysis supported by tests, or a test. Consult the linked page for a complete list.
You need to provide a representative structure for at least one ultimate load test (and more if you need to test for collective loads over a certain number of flight hours or number of cycles). Your assumed loading must also be checked and cleared by the authorities. Normally, your type certificate will only cover the flight hours and cycles which have been successfully tested, and this will be expanded as testing progresses.
Since your MoC list will have many points that will require a flight test, you need to perform this flight testing in close cooperation with the certification authorities.

Your first design will be the hardest. New applicants will be subject to detailed inspections while experienced DOs will be cut some slack if enough confidence in their abilities has been earned.
The really hard part will be the operation of an uncrewed aircraft in regular airspace because here the regulations have not been finalized. You will have to follow the rules for manned airplanes as outlined above. Most likely you will need to establish a restricted airspace for operations and make sure that your airplane will stay in this area.

This is about as good an answer as this question could get, but as the question is tagged [tag:faa] I'm not sure how useful EASA regulations will be.

@Jamiec True, but I'm much more familiar with EASA rules. However, FAA is not so different, except that they cut established manufacturers much more slack. Cough, cough Boeing Authorized Representatives, cough.


text:
What aircraft has a sustained bright orange light visible at night/early morning?
This morning around 6 a.m. in Durham, N.C. I was sitting on my porch and saw a bright orange light, I thought it was Mars it was so orange, but it was very bright.  After looking at it for a moment it briefly ascended and disappeared.  Now, there is no cloud cover, I just double-checked. What could this be?
My central heating system was also at a lull and making a weird noise I havn't heard it make and it started right back up when the thing disappeared.  Am I wiggin?  Did I see a UFO?
Edit: The direction of the light was southwest and it was not very high above the horizon, I am unable to give degrees as I don't know how, wish I did.  I did not have to look up, I was sitting as well and saw it quite easily without tilting my head.

"Did I see a UFO?" -> Yes, since you could not identify that flying object, you did indeed (by definition) see an Unidentified Flying Object (UFO). But most likely not an alien one xD

Lol, I guess that is why I want to see if anyone else may be able to point me in a direction of what it could be.  But yes, indeed, so far it's a UFO per definition :)  Thanks, I havn't seen anything like this before.   I mean, a single parachute flare perhaps?  It was pretty high up though.

Which direction was the light and estimated how high above horizon in degrees?  Question could be improved by this info.  PS a parachute flare would not be expected to ascend.

Could've been an older aircraft with the landing lights on - they tend to use halogen bulbs, rather than modern, white LEDs which can appear orange if conditions are right. The "ascending" could've been your perspective as it passed overhead (maybe you didn't hear it fly over because of your heating?)

The direction of the light was southwest and I am unable to quantify how high above the horizon in degrees as I am unsure how to do so.  It was not very high though, I did not have to tilt my head up at all, and I was sitting. I was also thinking of landing lights but the ascent doesn't make sense.  Are there also lights that go on after taking off? I believe so... That being said, I saw no blinking lights whatsoever in the presence of this large bright orange light.  Thank you for your feedback and questions.

If it was early morning you probably saw an aircraft which reflected the morning sun. Even if the sun has not yet come up on the ground, it may already illuminate aircraft at altitude. As soon as it is no longer illuminated, for example because of a cloud of simply the horizon between the sun and the aircraft, the glow will no longer be visible, and the lighting conditions may be such that the entire aircraft may no longer be discernible to the naked eye.
As to your central heating, try diy.stackexchange.com.

Re "As to your central heating, try diy.stackexchange.com."  +1 for most unusual answer ever given on ase...

However 6 AM is a long time before sunrise this time of year...

@quietflyer Dawn at Durham is around 6.55 which is close enough for me.

I think you are spot on. I see the same phenomena in the hills to the east of me when the sun sets. Usually 15 minutes before to 15 minutes after sunset depending on how high up the building are. I”m guessing it’s the sun reflecting off of the windows.

That's the way to see satellites or the space station, just before sunrise or after sunset. That leaves plenty of time to fix the heating.


text:
What is a typical fuel temperature entering the burner for different mission flight points of a civil aircraft?
Is there a target regarding the fuel temperature that enters the turbine engine's combustion chamber and if so does it change with different operation flight points in civil aircraft applications?
Is there an online source you can suggest so that I get a better understanding of the fuel temperature variation in a turbine engine, and specifically what is its condition before entering the aircraft's burner?
Thank you in advance!

Are you asking about piston or turbine engines?

Yeah i am sorry i did not clarify. I am talking about turbine engines.

The fuel is pretty warm, being heated by engine oil through a heat exchanger, but I can't remember if the fuel/oil coolers use thermostatic control to regulate the fuel temperature.  Do some searching around "fuel/oil cooler temperature control", or "thermostatic control" etc.


text:
Does a jet engine keep running when it can no longer be controlled from the cockpit?
On the Qantas Flight 32 incident, the Airbus A380's number two engine encountered an uncontained rotor failure and partially damaged the controls of number one engine as well.
According to Wikipedia, engines one and four entered a 'degraded mode' after the explosion, and number one could not be shut off after landing.
So it seems that in case an engine loses all communication signals from the aircraft's control systems in the cockpit, it could somehow remain operational.  To me that definitely sounds a lot safer compared to shutting down and risking losing all thrust.
So do jet engines, by design, keep producing thrust in case they lose contact with the control systems?

That depends on your definition of 'safer' - would you rather glide an A380 on zero power, or land one on full power? (My own preference would be full power, that way I can fly around above an airport until I run out of fuel, then glide to a landing)

This Citation even restarted after the pilot had left the cockpit. Lucky enough, the aircraft was in water :-)

General rule here: the engine will remain at its last power setting should the FADECs lose comms with the flight deck controls (in your A380 case) or the thrust lever cables come unhooked (in the case of an older aircraft with mechanical cable-and-pulley controls).
However, the fire handle will kill the engine even if the main controls fail -- it operates the firewall fuel and hydraulic shutoff valves.  In QF32, this didn't happen because the cable for the #1 engine fire handle itself was damaged by shrapnel entering the wing.

That sounds like a horribly bad design: an accident that causes an engine fire may also cause the fire suppression system to fail. The usual norm is fail-safe: if the safety shutoff valves become uncontrollable for whatever reason (implies significant unforeseen damage) then they should fail closed. Of course, this implies that there should be redundant control of those valves lest they become a SPOF for an engine.

@MSalters -- two points.  First is that an uncontained engine failure (such as QF32) is essentially a game of roulette as to what suffers from the shrapnel bombardment the plane just received -- one day it may be the fire handle cable for the engine next to it on the wing, the next day it might be a hydraulic line feeding the outboard slat actuator.  Second, engine mountings in modern jets are designed for the most part (center engines in trijets are the only exception that's newer than the very first jetliners) to come off the aircraft cleanly if they do experience an uncontrolled fire, AIUI.

@MSalters In this case it isn't clear whether fail closed is the fail safe option. If we were discussing  a power plant turbine or a ship board engine I'd agree. But in the unique operating envelope of an aircraft shutting an engine unwarranted may have equal or greater damage potential than not being able to shut down an engine.

@curious_cat Especially when it's the remaining engine on the side where you already lost one engine. QF32 would have been in serious trouble had the #1 engine shut down in flight. They were having a hard time controlling it as it was.

@reirab Good example. The point is that fail safe isn't always fail closed.

"In QF32, this didn't happen because the cable for the #1 engine fire handle itself was damaged by shrapnel entering the wing."  So why not put the valves in the fuselage (where they should be safe, or, at the very least, saf_er_, from engine shrapnel) rather than the wing?

@Sean -- because the valves need to be at the engine firewall in order to isolate the engine from the rest of the plane

@Sean Adding to what UnrecognizedFallingObject said, there's also a metric crapton of jet fuel in the wing tanks of many modern airliners. You'd need to cut off the engine feed from those tanks, and you might not want to pump all that into the fuselage and then back again just so you can have a cutoff valve within the fuselage (which may or may not do its job properly after an uncontained engine failure, even if it wasn't for the possibility of a fuel leak directly from the tanks...).


text:
Which external instruments are visible on the A350's nose section?
Most pictures of airliner's nose sections show small dark tube- or fin-shaped instruments sticking out of the fuselage below the cockpit windows.
For example this Airbus A350 shows them well:

Source: Airliners.net
Other airliners (737, A380, 787) carry similar instruments at the front.
I'm sure Google would be able to tell me if only I knew how to correctly phrase my question, but...
These instruments sticking out of the fuselage, what purpose do they serve?

I am not sure other planes have these. All of them have the instruments on the sides. But I don't remember seeing the ones in the centre anywhere else.

Now seeing the answer, indeed, every aircraft has a pitot tube (here mounted on the AoA vane to improve precision at high AoA), most have AoA vane and the faster ones have total air temperature probe (needed to derive Mach number), but sideslip vanes are not common. Most planes rely on a level or lateral axis of accelerometer in IRS for coordinating turns.

Why is there a hatch above the (FO's?) seat? Emergency escape?

@CGCampbell Yes, the A350 is the first Airbus with an escape hatch in the roof.

Here's a better picture showing all probes, and labeled:

Link to original, high-resolution, unnumbered picture
They are:

Ice detector
Multi-function probe 1
Static port
TAT probe
Side-slip vane
Pitot probe
Angle-of-attack vane

Airbus.com has a PDF (pdf page 125) about the various probes.

1
As the name suggests, the multi-function probes record different types of data. Here are more details:

The piloting of any aircraft involves knowing the relative speed of
  the aircraft with respect to the airflow surrounding it, that is to
  say to the relative wind. This speed is determined with the aid of
  sensors of the static pressure Ps, of the total pressure Pt and of the
  angle of incidence “alpha”. “Alpha” provides the direction of the
  speed vector in a reference system tied to the aircraft and Pt-Ps
  provides the modulus of this vector. The three aerodynamic parameters
  therefore make it is possible to determine the speed vector of an
  airplane.

These are covered by a US Patent.

Someone asked a similar question here.

#5 is a upgraded yaw string, invented by the Wright Brothers, and used on their 1902 glider.
http://upload.wikimedia.org/wikipedia/commons/5/50/Glider_Instrument_Panel.png

@rbp It looks awfully inconveniently positioned; I can't imagine it's very easy for the pilot to see in-flight, especially during maneuvering.

@MichaelKjörling All the marked items are merely sensors that feed data into the avionics.  The data is then calibrated (no sensor is 100% accurate) before being displayed in the flight deck on the instruments.

@ioctlLR Yes, my previous comment was tongue in cheek. I guess I didn't make that sufficiently clear.


text:
What do aerodynamic flow cones measure?
This picture of an Airbus A350 test aircraft shows multiple instruments on the flap fairings, wing fairing and on the empennage:

Source: A380_TLS_A350 AIB199GG (high-res version)
They are being described as 'aerodynamic flow cones'.
What are these -- what do they measure, and how?

Is there a chance you could find a better picture? At this scale we can't really see what those things are.

@Federico: I believe he speaks about the little shiny dots glued all over the airframe.

Looks like a fancy way of tufting.

To expand a bit on the other explanations here, "flow cones" are one of the many methods used for flow visualization.
When something is being tested in a wind tunnel or in flight, you usually can't see the air flow around the body. To be able to visualize the flow, something is added to the air, like smoke, or to the body, like flow cones or tufts. Tufts are basically just short lengths of string taped to the body at one end. Flow cones are small cones attached at their apex with string.
These items on the body have two main functions. Primarily, the flow cones or tufts will align them selves with the flow, allowing observers to see the direction of the air flow in that area.
They can also show flow separation. When the flow is attached to the body, it flows fairly smoothly along the surface. When the flow separates from the surface, it becomes much more turbulent and chaotic. The tufts or cones will show this as they are moved by the air.
Flow cones are larger than tufts, so they are much easier to see, which is important in cases like the picture you posted, where they will probably be observed from a chase plane at some distance.
For more on flow separation, see this question, or this video of tufts on a stalling wing. For a comparison of tufts and cones, zoom in on this photo of the X-29A. The darker, larger objects behind the cockpit are cones, while the reddish, smaller ones further aft are tufts. You can also see smoke at the nose being used to visualize the flow.

They are used to visualize the airflow over parts of the aircraft. See this document for more details about flow visualization techniques (flow cones are described at 2.2.1)


text:
How to simulate magnetometer used on navigation system?
Magnetometer is used to measure yaw angle which will be used on AHRS system.When I simulate the magnetometer in matlab, I feel confused about what unit should be used for measurements magnetometer?Should I use μT(microtesla),rad or degree?
I know in real world, the magnetometer is to measure earth magnetic field, so it should be μT. the reason that I feel confused is that:In some papers, their simulation says $B_{i}$(earth's magnetic field) is given by $[\frac{1}{\sqrt{2}},0,\frac{1}{\sqrt{2}}]$ or $[1;0;1]$,symmetry-preserving observer.page11 and they didn't give the unit of above vector. I also find a book, called Small Unmanned Aircraft: Theory and Practice, it introduced how to simulate IMU sensors and says the standard deviation and bias error of Magnetometer could be 0.3 degrees and 1 degree.
So I am totally confused about the unit and value of the earth's magnetic field or Magnetometer measurements.

It is impossible to answer this question without knowing what you want to achieve with your simulation. Are you analysing the electronics, are you developing navigation software, are you investigating the effect of magnetic anomalies on navigation performance, are you modeling the dynamic response of a magneto meter to a changing magnetic field, something else?

I am designing a estimator for the navigation system. so the measurements to my estimator are positions(GPS),acceleration(accelerometer),magnetic field(magnetometer).Right now I want to add some noise and bias to the measurements and see the estimation performance of the estimator. so in my case, I want to figure out the unit and value range of the magnetometer so that I can add the right noises.

The unit does not really matter if you measure the right quantity. But obviously angle magnetic induction and angle are different quantities. Typically—but it might depends on the type of magnetometer used and is not true e.g. of mechanical compass—there will be two or three magnetometers detecting components of the magnetic induction vector, and then you calculate the bearing to magnetic north, and if you have three components the inclination from those.
The raw output of an electric vector magnetometer, measuring one axis of the magnetic induction vector, will be a voltage. You can convert it to the inductance in μT or whatever unit, but for navigation you only care about the direction and the units cancel out when you calculate that so you don't have to.
For magnetometers intended for nagivation, the required accuracy is only specified for the angle, in degrees, because the magnitude is not used.

For my case, the magnetometer would be a MEMS electric  magnetometer. If a paper says $B_{i}$(earth's magnetic field) is given by $[\frac{1}{\sqrt{2}},0,\frac{1}{\sqrt{2}}]$ or $[1;0;1]$. Since they didn't give the unit, do you know the unit according to the values they give? is it μT, rad or degree?

@DarkKnight no, that would require more context.

hello, I have added more context,could you help me take a look?

I think I have found the answer why some papers didn't give the magnetic field vector. They have done some normalization.


text:
Given an exact date, time, and coordinate, can I locate a plane that flew overhead?
I need to identify an aircraft seen at 36.841900,-87.673600 Kentucky on July 4, 2020, at 12:29am.
Is there a way to do this feasibly?

Figured out what it is:

Is this not the same as your previous question?

@ThatCoolCoder - that could be said, but no I asked a new set of questions. Check the update.

Voting to close THAT question as a duplicate of this one. This is the better question, and there is no need for both to be open.

Your “figured out what it is” remark isn’t appropriate to include in the question.  If you like you can post a separate self answer that includes this information for the curious.  And choose your own answer as accepted.  P.S.  given your description in the other question, this calls into question your powers of observation...

I recommend using flightradar24. In addition to its many other features, it has a playback mode. I'm not sure if there is a simple way to view a specific coordinate; however it should be easy enough to navigate to your desired location using the map view. If looking at coordinates is a must, I have found that you can put them after the url like so:
https://www.flightradar24.com/-36.38,128.09
Edit
According to Jan Hudec, you need a flightradar24 subscription to access dates this old.

You'll need a subscription with a date that old though. For free, the playback only goes back 7 days.

If the spotting was close enough to an airport, https://webtrak.emsbk.com would have shown it, but unfortunately the playback only goes back two months there.


text:
Why would a plane have these lights on the bottom?
I'm trying to convince someone this is not a UFO but probably just not a commercial plane. What would be the reasons to have the colors of the plane lights like this?
The person is claiming because it was inaudible, seemed rather large, and had blinking lights that it is a UFO. Are there any reasons for this as well?
Coordinates: 36.841900,-87.673600 Kentucky
Time: July 4, 2020, 12:29am

Tell us the time and place, and we can likely find the exact aircraft.

@Camille Goudeseune This was in Tennessee. I am attempting to get the exact location and time this occurred. I'll report back once I have that. Thank you.

Welcome to Aviation SE, David!  FYI, on a Q&A site like this, when you have more info, it's good to edit your original question and put the info there, instead of tacking on more comments.  We look forward to solving the mystery...

@Camille Goudeseune The coordinates are  38.842, -87.674. Time: July 4, 2020, 12:29am.

If you cannot identify an object, and the object is flying, then it is, (by definition) an unidentified flying object.  That is not the same thing as confirming (or even suggesting) that it is a spacecraft from another galaxy.  ;)

It is likely not unidentified, but not identified by him lol.

Any additional information such as movement, duration, etc.?  July 4th makes it seem very likely that they were distant Chinese floating lanterns like these:  https://www.justartifacts.net/flskyla.html

@MichaelHall It was low to the ground, seemed fairly large (apparently), and made no noise. It seemed to flash as well and maintained a triangular position.

@CamilleGoudeseune My apologies for not correctly using the @ feature. I have updated the post to include the coordinates and time.

Those ETs use the same navigation lights than on Earth, red on left, green on right, and red blinking anticollision on the belly or the tail (rotated / annotated picture). They are not as smart as ET experts think, they need to copy our barely emerging civilization (maybe we can sue them for intellectual property laws infringement to give them a taste of who they will be dealing with).

@mins thanks so much for your reply! That explains a lot.


text:
Are there any plans to develop remote area escalator aerobridges?
Are there any remote stand applied to any size of aircraft that uses the mechanical movement which allows the steps to transfer passengers safely down or up without any efforts? In other words, an escalator that allows the passengers to use it to get-off or inside the aircraft in the remote stand area.

What airport or airports are you wanting to ask about?

Mobile escalators for passenger boarding exist. By the looks of the following image, they are not exactly a new invention:

(thyssenkrupp: The wondrous world of the escalator)
It seems, today they are mostly used in Saudi Arabia. Thyssenkrupp is still producing these for the Boeing 747SP:

(thyssenkrupp: Datenblatt Mobile Fahrtreppen)
According to this article, the Saudi royal family is also using mobile escalators by TEC Hünert:

The greatest possible degree of convenience for passengers when entering or leaving a parked aeroplane is almost certainly that provided by the mobile escalator version of the TEC Hünert passenger stairs. It enables the passengers to reach the aeroplane door with a minimum effort. The passenger is raised from the ground to the lowest part of the escalator by a lift installed in the place of some of the lower fixed steps. Furthermore there are other variations that for every order can be adapted flexibly. In particular for mobile escalators high-value components and materials are used to guarantee the highest level of comfort and passenger safety, ensuring an exclusive prestige object for every airport.

(TEC Hünert)